Apparatus for comminuting ores or the like



NOV. 20, 1962 A. c. DAMAN 3,064,906

APPARATUS FOR COMMINUTING ORES OR THE LIKE Filed Oct. 22, 1959 3 Sheets-Sheet 1 INVENTOR.

Arfhur C. Daman BY ATTORNEYS Nov. 20, 1962 A. c. DAMAN 3,064,906

APPARATUS FOR COMMINUTING ORES OR THE LIKE Filed 0612. 22, 1959 v 5 Sheets-Sheet 2 INVENTOR. g 4 Arfhur C. Damon w v firm a ATTORNEYS Nov. 20, 1962 A. c. DAMAN 3,064,906

APPARATUS FOR COMMINUTING ORES OR THE LIKE Filed Oct. 22, 1959 5 Sheets-Sheet 3 INVENTOR. Arfhur C. Daman ATTORNEYS United States Patent Office Patented Nov. 20, 1962 3,064,906 APPARATUS FUR COMMZNUTENG QRES OR THE LHKE Arthur C. Daman, Denver, Colo, assignor to Denver Equipment Company, Denver, Colo, a corporation of Colorado Filed Oct. 22, 1959, Ser. No. 848,142 17 Claims. (Cl. 2417l) This invention relates to apparatus for comminution of ores or the like and more particularly to ore beneficiation circuits involving a milling or grinding operation, and is a continuation-in-part of my copending application Serial No. 519,205, filed June 30, 1955 now Patent No. 2,948,481.

My invention relates to comminution mills for use in ore treatment wherein it is necessary to remove undesirable native materials such as clays, gypsum and certain insoluble impurities such as sulphates that, if not removed, will have a deleterious effect on subsequent treatments.

Many ores will contain native inclusions of waste materials such as clays, gypsum, and the like which are of extremely fine size and tend to form colloidal dispersions in the pulp in grinding operations. Materials, such as for example clays and other gangue constituents of the sylvinite ores of the Carlsbad, New Mexico field, will be re ferred to hereinafter as primary slimes. Other material, which is reduced to a relatively fine size in the grinding operation employed to unlock the valuable constituent from associated matter, will be hereinafter referred to as secondary slimes.

Primary slimes when with a liquid carrier, such as for example Water, are usually of a slimy or gummy consistency and impede the efficiency of equipment throughout the milling circuit and perform no useful function in the treament. Some operations provide a desliming treatment before a flotation separation for example, but are only eflfective in removing a portion of the primary slimes, leaving the remainder as a nuisance factor in subsequent processing stages.

An important function of this invention is to provide means for preliminary removal of the primary slimes from a comminuting apparatus before any substantial comminution has occurred.

Therefore, it is among the objects and advantages of this invention to furnish simple, efiicient and economical methods for elimination of a major portion of the primary slimes of an ore prior to the commencement of the pulp-forming or comminution stage of an ore beneficiation treatment so as to prevent intermingling of such primary slimes with other solids of the pulp in the grinding and subsequent stages of the circuit.

Another object of this invention is to provide simple, durable and eflicient equipment capable of removing a substantial portion of the primary slimes of an ore pulp substantially before the comminution operation.

Still another object of this invention is to provide means integral with a mill for the removal of undesirable primary slimes inclusive of means for inducing the passage of said slimes from the mill.

Still further objects reside in the novel details of construction and novel combinations and arrangements of parts which wil become obvious from a study of the fol lowing description with reference to the appended drawings in which:

FIG. 1 is a vertical central section through a rod mill representing one structural embodiment of this invention;

FIG. 2 is a vertical central section through a peripheral discharge mill incorporating features of the present invention;

FIG. 3 is a fragmentary vertical section through the feed end of a grinding mill of the type shown in FIG. 2, and is illustrative of another modified arrangement for primary slimes elimination;

FIG. 4 is a fragmentary vertical section through the feed end of a grinding mill of the type shown in FIG. 1;

FIG. 5 is a vertical central section through a peripheral discharge mill utilizing a modified form of primary slimes elimination;

FIG. 6 is a fragmentary end elevation of the grate unit of the mill of FIG. 2, partially broken to shown the arrangement of interior parts in section; and,

FIG. 7 is a section 7-7 of FIG. 2.

One of the novel features of my invention is the provision of means for tumbling the feed pulp to scrub the ore particles causing attrition to release the slime inclusion. Further, there is provided a novel separation and discharge for slimes. The structure by which the removal is accomplished is arranged in covering relation to the annular interior surface of the inlet trunnion and is adapted to pass primary slimes and rejectcoarser sizes in order that the primary slimes may be separated and removed before being subjected to any substantial impact or attrition influences within the mill. As generally shown in the drawings, the mill may comprise a charge of balls or rods of suificient length to at all times cover substantially the peripheral passage to the outlet and the spacing between the adjoining rods of the charge providing the desired degree of comminution.

' In the forms illustrated in FIGS. 1 and 2, there is a screening operation in the inlet trunnions as Well as the provision of a grate member at the mill end for added screening capacity to increase the efiiciency of the screening operation and more complete removal of the primary slimes. There is also shown a variety of passage arrangements for conducting and directing the slimes of discharge to appropriate outlets. Preferably but not necessarily, a spray unit may be disposed in the feed trunnions of the mills to accelerate the separation of primary slimes from the other ore constituents and thereby assist their entrainment in the flow to the slimes discharge outlet.

It is not necessary that the spraying feature be incorporated when there is suflicient tumbling of feed material in passage through the inlet trunnions to cause a sepa' ration of the primary slimes to occur directly from the flow through said tumbling area.

The mill of this invention is particularly useful in conjunction with flotation circuits, such as those using amines. In an amine circuit such as used in the treatment of sylvinite ores, if the clay slimes are not removed, the clay becomes the primary attracting material for the amine reagent rather than the cylvinite values. Also, when grinding pulp preparatory to a cyanide treatment, certain foreign constituents in the ore, such as oxidized constituents, may have a deleterious effect on the subsequent cyanide treatments. By use of my novel arrangement for the removal of primary slimes, it is possible to remove a major portion of these undesirable materials from the ore preparatory to cyanide treatment. Further, in the case of comminution of some soluble ores such as sulphates, a removal of a substantial portion of such undesirable constituents may be accomplished by use of the apparatus of this invention.

As shown in FIG. 1, a cylindrical mill, shown generally by numeral 12, has a shell 12a connected with a feed trunnion 13 adapted to be journaled in conventional manner. The mill is provided with a feed scoop i4 discharging into the feed trunnion. A discharge trunnion 15 is connected with the shell at the opposite end of the mill and is also adapted to be journaled for rotation in a conventional manner. The mill has the usual shell liners 16, a grate-type end liner l7 cooperating with a tumbling trunnion liner 18 in the feed end, a convenaoeaeoc tional trunnion liner 19 for the discharge end, and a gratetype end liner 20 having openings 21 at the discharge end.

In this assembly a spray pipe 28 having suitable openings 29 for spraying water or a similar material extends into the mill 12 through the feed trunnion 13 from a suitable source of supply (not shown). Conventional features of the mill construction, such as fastenings of heads, bolting of liner sections, location of manhole etc. have not been shown in order to more effectively set forth the novel arrangement of parts.

Annularly disposed on the interior surface of the inlet trunnion 13 is the grate member 18. Between the interior surface of the trunnion 13 and the member 18 is an annular space which connects with the space of the hollow end liner 17. These spaces are interconnected and define a discharge passage 31 for slimes to the outlet 26. Some of the released slimes enter passage 31 through the openings 32 of the annular trunnion grate 18 and additionally other slimes enter through openings 33 in the end grate 17 and are elevated by means such as lifter bars 131 (which are more clearly shown in FIG. 6). The lifter bars 131 (referring for the moment to FIG. 6) are radial bars or partition members which will operate to lift the entrained primary slimes to the passage 31 behind the hollow trunnion grate 18 for eventual delivery to the slimes discharge passageway 26. The operation of the lifting bars 131 may be compared to a Water Wheel which will lift water from a lower to a higher level by the rotation of the wheel. The capacity of slimes discharge provided by the arrangement of FIG. 1 is particularly suited to treatment of ores having a relatively large primary slimes content because of the large screening area afforded by the annular grating in the trunnion as well as the mill end grating 17.

In the operation of the mill of 'FIG. 1, after the passage of the material to be comminuted through the inlet trunnion and over the annular grating contained therein, the material passes through the mill and is comminuted by means such as grinding rods 27 for eventual passage through the openings 21 into the outlet trunnion for delivery to subsequent treatment stages (not shown). Reference character generally indicates the pulp level in the mill when it is in operation. The pulp (a suspension of ore in a media such as water) is delivered from the feed scoop 14 for flow through the hollow portion of the trunnion 13. Flow through the trunnion is assisted by the impelling influence of the tumbling flights 80 of the grate 18. Also, the tumbling aids in separation of slimes from the ore before it enters the mill 12 for the grinding operation. During its progress through the trunnion 13, the aforementioned spray 28 causes the feed to be subjected to a washing or scrubbing action in conjunction with the attrition resulting from the tumbling movement's through the inlet trunnion. As a consequence, much of the primary slimes present as surface contaminate on the particles of the pulp are loosened and/ or separated and suspended in the liquid medium. While this washing action is desirable with certain types of ores, it is not always necessary in order for the novel arrangement of parts herein set forth to satisfactorily operate and remove a major portion of the primary slimes.

Because there is a substantial head of liquid (indicated by reference character 30), there is a substantial time interval involved in material travel through the mill, and a portion of the primary slimes remaining in the pulp after passage through the trunnion will separate from the ore before substantial progression through the comminution zone. They, as well as some of what was formerly referred to as secondary slimes, will pass through the openings 33 of the end grating 17 for delivery through the discharge passage 26.

Consequently, a major portion of the grinding action involves substantially slime-free material and while additional secondary slimes may be produced in the grinding action, the slime content of the final discharge is not of such a character as to impede the efliciency of the subsequent treatments.

The features of my invention may be utilized in various types of mills, and FIG. 2 is illustrative of a pcripheral discharge mill embodying features of the invention. The mill 42 comprises a shell 42x interconnected with feed trunnions 43 at each end and each is provided with feed scoop 44. The mill is also provided with the usual liner assembly 46 and has hollow end grates 47 adjoining the tubular tumbling trunnion liners 48. Peripheral apertures 49 centrally of the mill pass pulp to a discharge outlet 50, the details of which will be subsequently described.

The hollow trunnion liner 48 has a series of apertures 51 which are sized to pass slimes and reject coarser sizes and the adjoining grate section 47 has similar apertures 52. The hollow portions of liner 48 and grate 47 provide a continuous passage '53 for directing the pulp passing said apertures through peripheral outlets 54 into a slimes outlet 55. The liners 48 are provided with steps 81 to impart the above referred to tumbling action and to impart progressive forward movement to the pulp. Spray pipes 56 having openings 57 therein for spraying to assist the tumbling action and separation of the primary slimes from other constituents of the ore. As was mentioned when referring to the mill of FIG. 1, a spray or wash is not necessary with some types of ores where the separation of primary slimes from the desired constituents may be accomplished alone by the tumbling afforded in the inlet trunnions. The separated slimes are entrained in a flow of liquid through the openings 51 and 52 and the major portion of the released slimes are thus conducted through the passages 53 and through apertures 54 to the slime outlets 55 without being subjected to any appreciable impact or attrition influences in the mill.

Thereafter, the action of the mill is directed to pulp which is substantially free of primary slimes and sized products will pass through openings 49 into the outlet 50.

The separated primary slimes may be passed to a dewatering stage and then wasted, and the product delivered via outlet 50 will be conveyed into the next stage of the circuit.

The mill is provided with parallel flanges 60a and 60b and an annular casing member 61 has flanged portions extending into parallel grooves in the flanges 60a and 60b as shown at 62 (FIG. 7). A close fit is provided and the pulp flowing out of any of the openings 49 is directed by casing 61 to the final point of discharge at outlet 50.

FIG. 3 illustrates a modified slime elimination arrangement using a grate assembly for a screening operation. In this modification, which may be incorporated into the structure of the mill shown in FIG. 1, a tumbling liner 18b adjoins an end grate 17b and the interior passage 31b terminates at a peripheral discharge which is in register with an outlet 26b, rather than the arrangement shown in FIG. 1 where the exit was 26. Slimes entering through orifices 33b of the liner flow to the end of passage 31b where a sectional discharge member 36 having dual restricted passages 37 controls the flow of slimes into the outlet 26b. The openings 37 in the members 36 may be closed when there is no discharge of slimes. The sizes of the passage 37 in the member 36 may be varied to accommodate the requirements of the particular operation. The member 36 may be used in any of the passage outlets of any of the modifications, where necessary, and the size of the passages 37 may also be varied as required to control the overflow through the said openings.

Another modification is shown in FIG. 4 and is particularly suited for the treatment of ores having a primary slimes content which loosens quickly after pulping. A tumbling trunnion liner 18c, having openings 32c, of a form similar to its counterpart shown in FIG. 1 and the slimes outlet 260 is located at the outer periphery of the trunnion; 18c. Preferably, the passage 31c of the trunnion liner is open at the mill end forming a skimmer 38c but may be closed by an extension of end liner 170 as indicated by the dash lines representation 390.

FIG. 5 illustrates another form of peripheral discharge mill embodying features of my invention. A mill 72 of this form is generally similar to the mill shown in FIG. 2 and comprises a shell 72x connected with right and left hand feed trunnions 73 each provided with suitable feed scoop 74. The shell has a usual liner 76, and end liners 77 adjoin and support a hollow trunnion liner 78 having raised portions 85 for inducing motion to the feed material. The openings 79 in the shell liner 76 permit discharge of the comminuted product into an outlet member 101. The trunnion liner 78 has a series of apertures 100 along its lengthwise extent which pass the primary slimes and reject the coarser sizes with the primary slimes resultantly flowing through the apertures 100 into the outlet 89. The incoming pulp may be sprayed Within the trunnion 73 by a spray pipe 86 which functions similar to that of the spray pipes of FIGS. 1 and 2.

In operation, pulp from scoop 74 is fed into the interior of trunnions 73 and is subjected, if desired, to the scrubbing action of the spray pipe 86 and the tumbling infiuence of the liner 78 so as to separate the primary slimes which are entrained for flow through apertures 100 and rapid passage to outlets 89 without being subjected to the impact and attrition influences of the mill. The mill may contain either a ball charge or a rod charge as required and the solids content will be sufliciently reduced in size by the time it has progressed from the end entrance to the central discharge so that it is substantially all within the required size range.

All of the foregoing arrangements may be selected and arranged in the various embodiments shown herein according to the requirements of a given treatment and would still be within the scope of the concepts of this invention.

From the foregoing it is readily apparent that the novel features of the present invention are applicable to a great variety of comminuting mills and circuits for ore beneficiation circuits incorporating such therein, and the structural embodiments shown and described herein are intended merely as indicative of one mode of practicing my invention and it is to be understood that it is not desired to be limited thereto but rather by the scope of the appended claims.

I claim:

'1. The combination with a rotary, drum-type grinding mill mounted for rotation about a substantially horizontal axis and having a feed trunnion at one end and a discharge outlet for ground product remote from said feed trunnion and an intermediate grinding section, of screening structure having portions arranged internally of the feed trunnion upstream from said grinding section and in covering relation to a slimes discharge outlet from the trunnion, and said screening structure being sized to pass slimes and reject coarser sizes in the flow of material traveling to said slimes outlet.

2. The combination with a rotary, drum-type grinding mill mounted for rotation about a substantially horizontal axis and having a feed trunnion at one end and a discharge outlet for ground product remote from said feed trunnion and an intermediate grinding section, of a screening structure arranged in the feed trunnion and within the mill at its feed end upstream from the grinding section of said mill in covering relation to a slimes discharge outlet from the trunnion and sized to pass slimes and reject coarser sizes in the flow of material traveling to said slimes outlet and means for scrubbing said pulp during its passage through said screening structure.

3. The combination with a rotary, drum-type grinding mill mounted for rotation about a substantially horizontal axis and having a feed trunnion at one end and a discharge outlet for ground product remote from said feed trunnion and an intermediate grinding section, of a screening structure arranged in the feed trunnion and within the mill at its feed end upstream from the grinding section of said mill in covering relation to a slimes discharge outlet and sized to pass slimes and reject coarser sizes in the flow of material traveling to said slimes outlet from the trunnion, means for scrubbing said pulp during its passage through said grate structure, and means for tumbling the pulp while passing through said trunnion.

4. The combination with a rotary, drum-type grinding mill mounted for rotation about a substantially horizontal axis and having a feed trunnion at one end and a discharge outlet for ground product remote from said feed trunnion and an intermediate grinding section, of screening structure arranged in the feed trunnion and arranged Within the mill at its feed end upstream from the grinding section of said mill in covering relation to a peripheral slimes discharge outlet from the trunnion and sized to pass slimes and reject coarser sizes in the flow of material traveling to said slimes discharge.

5. The combination with a rotary, drum-type grinding mill having an intermediate grinding section and mounted for rotation about a substantially horizontal axis and having a feed trunnion at one end and a discharge outlet for ground product remote from said feed trunnion, of a grate structure disposed in the feed trunnion in covering relation to a slimes discharge opening from the trunnion arranged to tumble incoming feed and sized to pass slimes and reject coarser sizes in the flow of material traveling to said slimes outlet.

6. The combination with a rotary, drum-type grinding mill having an intermediate grinding section and mountedfor rotation about a substantially horizontal axis and having a feed trunnion at one end and a discharge outlet for ground product remote from said feed trunnion, of a screening structure including a major portion internally of said trunnion in covering relation to a slimes discharge outlet from the trunnion and arranged to tumble incoming feed and sized to pass slimes and reject coarse feed in the flow of material traveling to said slimes outlet.

7. The combination of claim 6 in which the slimes discharge of a portion of the screening structure is in the feed end of the mill and is interconnected with the slimes discharges of the trunnion.

8. The combination of claim 7 in which the slimes outlet is on the mill periphery adjacent the feed end.

9. The combination of claim 7 in which the slimes discharge is from the trunnion and inclusive of means for inducing movement of separated slimes from the end of the mill to the trunnion discharge.

10. In a grinding mill having a feed trunnion at one end, a discharge trunnion at its oposite end and an intermediate grinding section, the improvement which comprises a tubular liner for the feed trunnion having orifices and raised portions arranged to tumble incoming feed and the orifices being of a size to pass slimes and reject coarser solids of pulp fed into said trunnion, and structure defining a peripheral outlet in said trunnion arranged to collect the pulp passing said orifices and to conduct it into the peripheral outlet from the trunnion.

11. In a grinding mill having a feed trunnion at one end, a discharge trunnion at its opposite end and an intermediate grinding section, the improvcment which comprises a tubular liner for the feed trunnion having orifices of a size to pass slimes and reject coarser solids of pulp fed into said trunnion, an end grate in the mill adjoining the tubular liner and having orifices of a size to pass slimes and reject coarser solids of pulp fed into said trunnion, and structure defining a peripheral outlet in said trunnion arranged to collect the pulp passing said orifices and to conduct it into the peripheral outlet from the trunnion. i

12. In a grinding mill having a feed trunnion at one end, a discharge trunnion at its opposite end and an intermediate grinding section, the improvement which 6 comprises a tubular liner for the feed trunnion having orifices of a size to pass slimes and reject coarser solids of pulp fed into said trunnion, means associated with said trunnion liner and arranged to tumble incoming feed for separating primary slimes from other ore constituents within the trunnion, and structure defining a peripheral outlet in said trunnion arranged to collect the pulp passing said orifices and to conduct it into the peripheral outlet from the trunnion.

13. In a grinding mill having a feed trunnion at at least one end, a peripheral discharge outlet for finished product distant therefrom and an intermediate grinding section between said trunnion and said outlet, the improvement which comprises screening structure at the feed end of the mill including portions in said feed trunnion arranged to pass slimes from the trunnion and reject coarser sizes of the feed, means defining an outlet to receive pulp passing the screening structure, and means for comminuting pulp between the screening structure and said outlet,

14. The mill as defined in claim 13 including a feed trunnion at each end of the mill, and a peripheral outlet centrally of the mill and inclusive of screening portions in each of said trunnions.

15. In a grinding mill having a feed trunnion at one end, and another trunnion at its opposite end, a grate member at the discharge end operating With the latter to discharge finished product from the mill and an intermediate grinding section between said trunnions, screening structure disposed Within said mill and adjacent the feed trunnion arranged to pass slimes and to reject coarser sizes of the feed into the intermediate grinding section, and means defining an outlet from the mill positioned to receive and discharge slimes passing through said screening structure.

16. The combination with a rotary, drum-type grinding mill mounted for rotation about a substantially hori-- zontal axis and having a feed trunnion at one end and a discharge outlet for ground pro-duct remote from said feed trunnion and an intermediate grinding section, of screening structure having portions arranged internally of and coextensive with the feed trunnion upstream from said grinding section and in covering relation to a slimes discharge outlet, and said screening structure being sized to pass slimes and reject coarser sizes in the flow of material traveling to said slimes outlet.

17. The combination with a rotary, drum-type grinding mill mounted for rotation about a substantially hori zontal axis and having a feed trunnion at one end and a discharge outlet for ground product remote from said feed trunnion and intermediate grinding section, of a screening structure in covering relation to a slimes discharge outlet from the trunnion, a portion of said screening structure being arranged internally of the feed trunnion upstream from said grinding section, and said screening structure being sized to pass slimes and reject coarser sizes in the flow of material traveling to said slimes out,- let.

References Cited in the tile of this patent UNITED STATES PATENTS 1,272,801 Hardinge July 16, 1918 1,381,987 Gordon et a1 June 21,1921 2,560,972 Martin July 17, 1951 

